Electron discharge tube



June 2, 1936. w. 1.. KRAHL- ELECTRON DISCHARGE; TUBE Filed Jul 17, 1955 INVENTOR BY W ATTORNEY Patented June 2, 1936 UNTED. STATES ELECTRON DISCHARGE TUBE Walter L. Krahl,

Hygrade Sylvania O a corporation Application July 17,

9 Claims.

This invention relates to space discharge tubes, and with particularity to an improved form of electrode support for devices having a heatable filamentary member.

In certain types of space discharge tubes, such for example in electron discharge tubes as ordinarily employed in radio receiving and transmitting apparatus, it is customary to provide means to support and space a plurality of electrodes in such a way that the electrical and mechanical character'stics are not disturbed by mechanical vibrations or the like. This is particularly true in the case of those devices employing a filament which is adapted to act either as a heater member or as an electron emitter. In tubes employing a filament of v or M shaped configuration, means are usually employed to maintain the filament taut, especially when the filament is at a relatively high operating temperature. Many methods of supporting such filaments have been proposed, but the most common one employs a tension hook or spring which engages the bight of the filament. One of the difiiculties with the usual type of resilient spring or hook support is that it tends to twist the filament out of its planar position so that as the filament expands in length at different temperatures, it tends to change its centering or spacing with relation to the other electrodes of the tube.

Accordingly it is a principal object of this invention to provide a novel means for supporting a filamentary member for space discharge tubes, whereby the above noted and other disadvantages are overcome. 7

Another object is to provide an improved manner of resiliently supporting a filament whereby more accurate alignment or centering of the filament may be attained. I

A feature of the invention relates to the novel organization, arrangement and relative location of parts which go to make up an improved filament support and assembly, for use in electron discharge tubes andthe like.

Other features and advantages not specifically enumerated will be apparent after a consideration of the following descriptions and the appended claims.

While the invention is of prime importance as applied to electron discharge devices such as radio tubes and the like, it will be understood that it is equally well applicable to other types of devices employing a heatable filament which is required to be kept under tension and with the various parts of the filament in substantial Swampscott, Mass., assignor to orporation, Salem, Mass.,

of Massachusetts 1935, Serial No. 31,764 (01. 25027.5)

planar alignment. Therefore while the drawing shows the invention embodied in one specific type of radio tube structure, it will be understood that this is done merely for purposes of explanation and not by way of limitation.

In the drawing, Fig. 1, illustrates in vertical section a radio tube mount embodying features of the invention.

Fig. 2 is a side elevational View of the filament assembly according to the invention.

Fig. 3 is a top plan view of one of the spacer members of the tube shown in Fig. 1.

Fig. 4 is an enlarged view of a modified form of filament guide rod'and hook according to the invention.

Referring to the drawing, the numeral 1 repre sents in dotted outline one well known form of enclosing envelope such as is employed in present day radio tubes. The envelope is sealed to a reentrant portion 2 terminating in a press 3 wherein are sealed the various lead-in and support wires 4 to 1 inclusive. Supported on and fastened to the wires 4 and 1 by any suitable means, as for example by eyelets 8 to I l inclusive, are electrode spacer members I2, l3. These spacer members may be of any suitable insulating material such as mica, lavite as ordinarily employed for this purpose in radio tubes. Each of the spacer members l2, I3 is provided with two perforations l4, l5, the perforations in member I2 being in vertical alignment with the corresponding perforations in member E3. The spacer l2 is also provided with an additional set of perforations l6, I! as shown in detail in Fig. 3. Positioned for sliding movement in the perforations M, I 5 are two filament support rods I8, I 9, each rod having its upper end bent over to U-shaped formation with the vertical part l8 of the bend parallel'to the rod proper. Surrounding each of the rods at its upper end are coiled springs 20, 2| which at their lower ends are seated against the member I2, while the upper ends of these springs may be fastened in any suitable manner, as by welding, to the respective rods. The horizontal part 22 of each rod has fastened thereto in any suitable manner downwardly depen'ding short hooks 23, 24, which hooks are adapted to engage the bight portions of the filament, the hooks passing through corresponding openings 25, 26 in disc l2.

As shown in Fig. 1 the filament may consist of a wire 0r ribbon bent to substantially an inverted' M formation withthe bight portions of the M engaging the respective hooks 23, 24. The free ends of the filament may be anchored 2 in any convenient manner to the lower spacer member l3. Thus as indicated in the drawing the member I3 is provided with metal tabs 21, 28 to which the free ends of the filament may be clamped or welded. For the purpose of passing current through the filament the lead-in wires 5, 6 may be clamped or welded to the members 21, 28 as indicated.

With the above described arrangement the rods 18, I9 are substantially free to slide in the direction of their length and are normally im-. pelled to an upward position by the springs 20, 2|.

' By reason of the engagement of the. portions l8- of the rods with the perforations l6, I'l the said rods are prevented from turning while they are sliding. Consequently as the filament expands while being heated, it is maintained under the proper tension and since the support rodsare guided in their movement there is substantially negligible tendency for the filament to be twisted out of its planar formation, with respect to the tubular anode.

While the drawing shows the invention embodiedin a tube of the two-electrode type, it will be understood that it. is equally well applicable to any other type of tube. Furthermore while the hook members 23, 24 are separate members attached to the guiding rods, it will be understood that if desired the U-shaped ends of the rods may have hooked end portions to engage the bights of the filament as indicated in Fig. 4. Other changes and modifications may be made herein without departing from the spirit and scope of the invention.

What I claim is:

l. A filament assembly for space discharge tubes comprising an insulator member, a guide rod mounted for sliding movement through said member, said rod having a projection engaging said member to prevent said rod turning, a hook carried by said rod and engaging the filament, and means engaging said rod to maintain said filament taut.

2. A filament assembly for space discharge tubes comprising a pair of spaced insulator members, a filament positioned between said members and having one end anchored to one of said members, a rod mounted for sliding movement through said members, a projection on said rod engaging one of said members to prevent said rod turning, a hook carried by said rod and engaging the other end of said filament, and a spring engaging said rod and one of said members to maintain the filament taut.

3. A filament assembly for space discharge tubes comprising a pair of spaced parallel insulator members, a filament having a V-shaped portion positioned between said members, a rod mounted for sliding movement through said members, said rod having an offset portion engaging an opening in one of said members to prevent said rod turning, a spring normally impelling said rod to raised position and a hook carried by said rod and engaging the bight of said filament.

4. A filament assembly for space discharge tubes comprising a rigid frame consisting of a pair of uprights and a pair of transverse members, a guide rod mounted for sliding movement through said members, a filament having one end anchored to one of said members and the other end connected to said rod, and spring means connected to said rod and abutting against one of said members to maintain said filament taut.

5. A filament assembly for space discharge tubes comprising an insulator member, an opening in said member, a guide rod mounted for sliding movement through said opening, another opening in said member, said rod having an offset portion arranged for sliding movement therethrough to prevent anchoring one end of the filament, means to connect the other end of the filament to said rod, and spring means acting on said rod to maintain said filament taut.

6. A device for resiliently supporting a filament comprising a member having a pair of perforations, a filament guide rod slidably passing through one of said perforations and having a portion bent back upon itself and slidably passing through the other of said perforations, and means for attaching a filament to said rod.

'7. A device for resiliently supporting a filament comprising a frame comprising a pair of vertical uprights and a pair of transverse members, a pair of perforations in each of said transverse members, the perforations in one member being in substantial vertical alignment with the corresponding perforations in the other member, a pair of rods slidably mounted to pass through said perforations, spring means normally impelling said rods to raised position, another pair of perforations in one of said transverse members, said rods having bent back portions passing through said other pair of perforations, and filament engaging hook members carried by said rods.

8. A radio tube mount comprising a press, a pair of uprights sealed into said press, and a pair of transverse insulator members fastened to said uprights, a filament having a V-shaped section positioned between said transverse members, the free ends of the filament being anchored to the lower one of said transverse members, a rod extending between said spacers and slidably pass ing through openings therein, the end of said rod being hooked and having the hooked end passing slidably through a corresponding openingv in one of said members, a spring having one end fastened to said rod and the other end seated against one of said transverse members to impel said rod upwardly and a filament hook carried by said rod and engaging the bight of the filament.

9. Amount for a radio tube comprising a V- shaped filament, a pair of uprights, an insulator member extending transversely across said uprights, a U-shaped member mounted for sliding movement in said insulator member, a spring having one end engaging said U-shaped member and the other end engaging said insulator member, a hook carried by said U-shaped member and engaging the bight of the filament.

WALTER L. KRAHL.

said rod turning, means for- 

